Intermediates for preparing 7-acyl-3-(sulfoalkyl substituted oxadiazolylthiomethyl)cephalosporins

ABSTRACT

The compounds of this invention are cephalosporins having various acyl substituents at the 7-position and a sulfoalkyl substituted oxadiazolylthiomethyl group at the 3-position of the cephem nucleus and intermediates for the preparation thereof. The 7-acylated compounds have antibacterial activity.

This is a division of application Ser. No. 666,095 filed Mar. 11, 1976,now U.S. Pat. No. 4,041,162.

This invention relates to a new series of cephalosporin compounds whichhave antibacterial activity when administered parenterally and tointermediates for the preparation thereof. In particular, the structuresof the biologically active cephalosporin compounds of this invention arecharacterized by having a novelly substituted oxadiazolythiomethyl groupat the 3-position of the cephem nucleus. Also, this invention extends tomethods and compositions for treating certain bacterial infections usingthese new compounds as well as to certain chemical intermediates andmethods for preparing the compounds described hereafter.

The compounds of this invention are represented by the followingstructural formula: ##STR1## in which: R¹ is an acyl group selected fromthe group consisting of: ##STR2## where: X is thienyl, dihydrophenyl,phenyl or phenyl mono-substituted with hydroxy, hydroxymethyl,formamido, ureido or carboxymethylamino;

A is NH₂, OH, COOH or SO₃ H; or formyloxy when X is phenyl;

Y is cyano, aminomethylphenyl, sydnone, pyridone, thienyl or tetrazolyl;

Z is methyl, trifluoromethyl, trifluoroethyl, pyridyl or cyanomethyl;

m is 0 to 2; and

n is 1 to 5,

Or a non-toxic pharmaceutically acceptable salt thereof.

It will be recognized that the 4-carboxylic acid group of the compoundsof Formula I may be readily esterified by methods well known to the art.These esters include, for example, simple alkyl and aryl esters as wellas esters which are easily cleaved, within the body, to the parent acidsuch as indanyl, pivaloyloxymethyl, acetoxymethyl, propionyloxymethyl,glycyloxymethyl, phenylglycyloxymethyl and thienylglycyloxymethyl estersand others. Of course, when A is COOH, this group may be similarlyesterified. All such esters are included within the scope of thisinvention.

Preferred compounds of this invention are represented by Formula I wheren is one.

Advantageous compounds of this invention are represented by Formula Iwhere n is one and R¹ is ##STR3##

Most advantageous are the compounds represented by Formula I where n isone, R¹ is ##STR4## X is phenyl or hydroxyphenyl and A is NH₂ or OH.

Examples of the most preferred 7-acyl substituents (R¹ NH--) of thecompound of Formula I are listed below:

α-hydroxyphenylacetamido

α-aminophenylacetamido

α-amino-4-hydroxyphenylacetamido

trifluoromethylthioacetamido

methylthioacetamido

2,2,2-trifluoroethylsulfinylacetamido

cyanoacetamido

α-carboxythienylacetamido

α-carboxyphenylacetamido

α-sulfophenylacetamido

methylsulfonylacetamido

cyanomethylthioacetamido

α-amino-4-carboxymethylaminophenylacetamido

2-aminomethylphenylacetamido

3-sydnoneacetamido

1-tetrazolylacetamido

2-thienylacetamido

2-pyridoneacetamido

4-pyridoneacetamido

4-pyridylthioacetamido.

Particularly preferred is the compound7-D-mandelamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid.

Cephalosporin derivatives having 7-acyl substituents as defined aboveare well documented in the prior art. Substitution by variouslysubstituted S-heterocyclicthiomethyl groups (--CH₂ SHet) at the3-position of the cephem nucleus, including carboxylic acid substitutedheterocycles, is also known. However, no references to cephalosporincompounds containing the 3-(sulfoalkyl substitutedoxadiazolyl)thiomethyl moiety disclosed herein are believed to be knownto the art.

The compounds of Formula I are preferably prepared by acylating7-aminocephalosporanic acid with an appropriately protected acylatingagent and then displacing the 3-acetoxy group with the desiredsubstituted oxadiazole thiol with subsequent removal of the protectivegroup(s). The sulfoalkyloxadiazole thiols of the formula: ##STR5## inwhich n is 1 to 5, are also objects of this invention, being importantintermediates for producing pharmaceutical end products as describedherein.

The carboxylic acid group of the acylating agent is activated by any ofthe standard methods such as conversion to the mixed anhydride, acidchloride, acid imidazolide or activated ester. In addition, a reagentsuch as dicyclohexylcarbodiimide can be used provided that the carboxylgroup on the cephem nucleus is protected with an easily removableprotecting group such as a benzhydryl, t-butyl, trichloroethyl, benzyl,benzyloxymethyl, p-methoxybenzyl or p-nitrobenzyl ester. When A is NH₂,the α-amino group of the acylating agent is, preferably, protected priorto acylation with an easily removable protective group known in the artsuch as t-butoxycarbonyl, trichloroethoxycarbonyl, benzyloxycarbonyl,the methyl acetoacetate adduct or similar groups commonly used in thesynthesis of peptides.

Alternatively, the compounds of Formula I are prepared by acylation, asdescribed above, of an appropriate 7-amino-3-(substitutedoxadiazolylthiomethyl)cephalosporin nucleus of Formula III: ##STR6## inwhich: n is 1 to 5; and

R² is hydrogen or a protecting ester group,

with an appropriate acylating agent followed by removal of theprotective groups when present. The compounds represented by Formula IIIare also considered as objects of this invention.

The protective groups can be removed according to methods well known tothe art, such as with trifluoroacetic acid when t-butyl ort-butoxycarbonyl protective groups are used. The resulting salt isconverted to the zwitterionic product or to the free acid by means of abasic ion exchange resin such as polystyrene-amine ion exchange resin(Amberlite IR-45) or else by basification of an aqueous solution of thesalt.

The acylating agents used as starting materials are either known orprepared by known methods.

The 7-amino-3-(substituted oxadiazolythiomethyl)cephalosporin startingmaterials of Formula III are prepared via reaction of7-formamidocephalosporanic acid, prepared by reaction of7-amino-cephalosporanic acid with formic acid and acetic anhydride, anda substituted oxadiazole thiol of Formula II followed by treatment withacid such as hydrochloric acid to remove the formyl group.

The sulfoalkyl substituted oxadiazole thiols are prepared by cyclizationof the corresponding 2-(sulfoalkylcarbonyl)hydrazinecarbodithioic acids,preferably as the potassium or sodium salts, such as2-(sulfoacetyl)hydrazinecarbodithioic acid dipotassium salt. The2-(sulfoalkylcarbonyl)hydrazinecarbodithioic acids are prepared byconversion of a chloroalkanoic acid ester, such as ethyl chloroacetate,to a sulfoalkanoic acid ester which is subsequently treated withhydrazine to give a sulfoalkanoic acid hydrazide which upon treatmentwith carbon disulfide and base gives the desired2-(sulfoalkylcarbonyl)hydrazinecarbodithioic acid.

Certain compounds of this invention are capable of forming salts with,for example, the alkali metals such as sodium or potassium, the alkalineearth metals such as calcium or with the ammonium cation. When A is NH₂,the compounds can exist as the zwitterion or as either an acid or basesalt. These salts are prepared by standard methods using a wide varietyof non-toxic pharmaceutically acceptable acids and bases known in theart and are also considered as objects of this invention.

It will be recognized that due to the asymmetric α-carbon atom in the7-acetamido group of Formula I when R¹ is ##STR7## optical isomers willexist. Racemic or resolved products are obtained depending upon whethera racemic or resolved sidechain acid is used as an acylating agent. Theresolved sidechain acids are readily obtained from the racemic compoundsby resolution according to well known methods, including fractionalcrystallization of a salt formed with an optically active acid or base.All of the isomers, including separated isomers and mixtures thereof,are included within the scope of this invention.

The compounds of Formula I have exceptional antibacterial activityagainst both Gram-positive and Gram-negative organisms. Minimuminhibitory concentrations (MIC's) range from 0.2 to >200 μg./ml. in invitro testing. Test results for the compound7-D-mandelamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid are given below:

    ______________________________________                                        Bacteria              MIC (μg./ml.)                                        ______________________________________                                        S. aureus HH 127      3.1                                                     S. aureus SK 23390    1.6                                                     S. villaluz SK 70390  200                                                     Strep. faecalis HH 34358                                                                             50                                                     E. coli SK 12140      1.6                                                     E. coli HH 33779      3.1                                                     Kleb. pneumo. SK 4200 1.6                                                     Kleb. pneumo. SK 1200 0.8                                                     Salmonella ATCC 12176 1.6                                                     Shigella HH 117       0.8                                                     Pseudo. aerug. HH 63  >200                                                    Serratia marc. ATCC 13880                                                                           100                                                     Proteus morgani 179    25                                                     Entero aergo. ATCC 13048                                                                            3.1                                                     Entero. cloacae HH 31254                                                                            1.6                                                     ______________________________________                                    

In the in vivo mouse protection test,7-D-mandelamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid exhibited ED₅₀ 's of 1.56 mg./kg. against E. coli 12140 and 1.56mg./kg. against Kleb. pneumo. 4200 upon subcutaneous injection.

Pharmaceutical compositions having antibacterial activity which comprisea pharmaceutical carrier containing an active but non-toxic quantity ofa compound of Formula I as well as methods of combatting bacterialinfections by administering such a composition to an infected host in anon-toxic amount sufficient to combat such infections are also objectsof this invention. Administration is preferably by parenteral injectionsuch as subcutaneously, intramuscularly or intravenously of suitablyprepared sterile solutions or suspensions containing an effective,non-toxic amount of the new cephalosporin compound.

The compounds of Formula I are formulated and administered in the samemanner as other cephalosporins. The dosage regimen comprisesadministration, preferably by injection, of an active but non-toxicquantity of a compound of Formula I selected from the dosage unit rangeof from 100 to 1000 mg. with the total daily dosage regimen being from400 mg. to 6 g. The precise dosages are dependent upon the age andweight of the subject and on the infection being treated and can bedetermined by those skilled in the art based on the data disclosedherein compared with that available to the art attained with knowncephalosporins.

The following examples illustrate the invention but are not to beconstrued as limiting the scope thereof. Temperatures are in degreesCentigrade (° C.) unless otherwise stated.

EXAMPLE 17-D-Mandelamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

To a solution of 237 g (1.5 mol) of potassium sulfite in 150 ml of waterwas added 183 g (1.5 mol) of ethyl chloroacetate. The reaction mixturewas refluxed for 4 hours then cooled and the solid was collected byfiltration. Recrystallization from 70% ethanol gave the potassium saltof ethyl sulfoacetate.

A mixture of 148.7 g (0.72 mol) of the potassium salt of ethylsulfoacetate and 32 g (1.0 mol) of hydrazine in 600 ml of water wasrefluxed for 12 hours. The solution was evaporated and the residualsyrup was dissolved in 200 ml of water. The aqueous solution wasfiltered, diluted with methanol to turbidity and then cooled. The solidwas collected by filtration and dried in vacuo to give sulfoacetylhydrazide potassium salt (69%).

C₂ H₅ N₂ O₄ S . K --Calculated: 12.50%,C; 2.62%,H; 14.57%,N. Found:12.66%,C; 2.75%,H; 14.71%,N.

To 91.9 g (0.478 mol) of sulfoacetyl hydrazide potassium salt was addeda solution of 31.0 g (0.478 mol) of potassium hydroxide in 400 ml ofwater containing 225 ml of ethanol. The mixture was cooled to 5°-10° and34.5 ml (0.574 mol) of carbon disulfide was added dropwise over a 10minute interval. The mixture was stirred in the cold for 20 minutes thenat ambient temperature for 12 hours. Ethanol (150 ml) was added and themixture was cooled in ice. The precipitate was collected by filtration,washed with ethanol and air dried to give2-(sulfoacetyl)hydrazinecarbodithioic acid dipotassium salt (81%).

C₃ H₄ N₂ O₄ S₃ . 2K --Calculated: 11.76%,C; 1.32%,H; 9.14%,N. Found:11.59%,C; 1.67%,H; 9.18%,H.

A solution of 50.0 g (0.163 mol) of2-(sulfoacetyl)hydrazinecarbodithioic acid dipotassium salt in 800 ml of1:1 ethanol-water was refluxed for 12 hours. The mixture was evaporatedto dryness and the residue was recrystallized from water to give2-sulfomethyl-1,3,4-oxadiazole-5-thiol potassium salt, m.p. 276°-278°(dec.).

C₃ H₃ N₂ O₄ S₂ . K --Calculated: 15.38%,C; 1.29%,H; 11.96%,N. Found:15.19%,C; 1.30%,H; 12.04%,N.

A solution of 2-sulfomethyl-1,3,4-oxadiazole-5-thiol potassium salt inwater is passed through an Amberlite IR-120OH ion exchange resin columto give, after lyophilization, 2-sulfomethyl-1,3,4-oxadiazole-5-thiol.

A mixture of 2.34 g (0.01 mol) of 2-sulfomethyl-1,3,4-oxadiazole-5-thiolpotassium salt, 0.84 g (0.01 mol) of sodium bicarbonate and 2.85 g(0.0067 mol) of 7-D-mandelamidocephalosporanic acid sodium salt in 50 mlof water was stirred at 65°-68° for 5 hours. The reaction mixture wastreated with 58.4 g of sodium chloride and additional water to give anearly saturated solution and filtered. The filtrate was passed througha XAD-7 resin column with water as the eluant. The product-containingfraction was lyophilized and the lyophilized material was reprecipitatedfrom methanol-water. The product was collected by filtration, washedwith ether, taken up in water and lyophilized to give7-D-mandelamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid disodium salt.

C₁₉ H₁₆ N₄ O₉ S₃ . 2 Na . 2.5 H₂ O --Calculated: 36.13%,C; 3.35%,H;8.87%,N. Found: 36.53%,C; 3.54%,H; 7.75%,N.

An aqueous solution of7-D-mandelamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid disodium salt is passed through a column of Amberlite IR-12OH ionexchange resin to give the title compound.

EXAMPLE 27-(D-α-Aminophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

A solution of 7.58 g (0.015 mol) of7-(D-α-t-butoxycarbonylaminophenylacetamido)cephalosporanic acid, 1.96 g(0.01 mol) of 2-sulfomethyl-1,3,4-oxadiazole-5-thiol and 2.94 g (0.035mol) of sodium bicarbonate in 125 ml of water is stirred at 60° for 5hours while maintaining the pH at 7.0-7.2 by addition of sodiumbicarbonate. The mixture is cooled and extracted with ethyl acetate. Theaqueous phase is acidified to pH 2.5 with 3N hydrochloric acid and theacidic solution is extracted again with ethyl acetate. The aqueous phaseis brought to pH 7.1 by addition of 5% sodium carbonate solution, thenpassed through a XAD-4 ion exchange resin column and eluted with waterand methanol to give7-(D-α-t-butoxycarbonylaminophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid disodium salt.

7-(D-α-t-Butoxycarbonylaminophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid disodium salt is stirred at 25° with 25 ml of trifluoroacetic acidand 25 ml of 1,3-dimethoxybenzene for 2.25 hours. The mixture isevaporated to dryness, ether is added to the residue and the precipitateis collected, washed with ether, stirred in acetonitrile for 2 hours anddried in vacuo to give the title compound as the trifluoroacetic acidsalt.

An aqueous solution of the trifluoroacetic acid salt is brought to pH5.0 by addition of dilute aqueous sodium hydroxide. Afterlyophilization, the lyophilized material is dissolved in methanol andether is added to precipitate7-(D-α-aminophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid sodium salt. The sodium salt is dissolved in water and the aqueoussolution is passed through an Amberlite IR-120H ion exchange resincolumn. Lyophilization of the eluted material gives the title compound.

EXAMPLE 3

Reaction of the N-t-butoxycarbonyl derivative of the followingcephalosporanic acids:

7-(α-amino-4-hydroxyphenylacetamido)cephalosporanic acid

7-(α-amino-4-formamidophenylacetamido)cephalosporanic acid

7-(α-amino-3-formamidophenylacetamido)cephalosporanic acid

7-(α-amino-4-ureidophenylacetamido)cephalosporanic acid

7-(α-amino-3-ureidophenylacetamido)cephalosporanic acid

7-(α-amino-4-hydroxymethylphenylacetamido)cephalosporanic acid

7-(α-amino-1,4-cyclohexadienylacetamido)cephalosporanic acid

7-(α-amino-4-carboxymethylaminophenylacetamido)cephalosporanic acid

with 2-sulfomethyl-1,3,4-oxadiazole-5-thiol and sodium bicarbonate asdescribed in the procedure of Example 2 followed by removal of theprotective group and conversion of the trifluoroacetic acid salts to thefree acids as described therein gives the following compounds of thisinvention:

7-(α-amino-4-hydroxyphenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-amino-4-formamidophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-amino-3-formamidophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-amino-4-ureidophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-amino-3-ureidophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-amino-4-hydroxymethylphenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-amino-1,4-cyclohexadienylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-amino-4-carboxymethylaminophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid.

EXAMPLE 4

7-(4-Hydroxymandelamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid is prepared by reaction of 7-(4-hydroxymandelamido)cephalosporanicacid sodium salt and 2-sulfomethyl-1,3,4-oxadiazole-5-thiol followed bytreatment of the product with Amberlite IR-120H ion exchange resin asdescribed in the procedure of Example 1.

EXAMPLE 5

When the sodium salt of a cephalosporanic acid listed below:

7-(3-sydnoneacetamido)cephalosporanic acid

7-(2-thienylacetamido)cephalosporanic acid

7-(1-tetrazolylacetamido)cephalosporanic acid

7-(2-aminomethylphenylacetamido)cephalosporanic acid

suitably protected as necessary, is reacted with2-sulfomethyl-1,3,4-oxadiazole-5-thiol by the procedure described inExample 1 and the product is deblocked when necessary and converted tothe free acid as described therein, the following compounds of thisinvention are obtained, respectively:

7-(3-sydnoneacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(2-thienylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(1-tetrazolylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(2-aminomethylphenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid.

EXAMPLE 67-Trifluoromethylthioacetamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

A solution of 1.96 g (0.01 mol) of2-sulfomethyl-1,3,4-oxadiazole-5-thiol, 4.36 g (0.01 mol) of7-trifluoromethylthioacetamidocephalosporanic acid sodium salt and 1.68g (0.02 mol) of sodium bicarbonate in 50 ml of water is heated at 70°for 5.5 hours while maintaining the pH at 7.5 with 5% aqueous sodiumbicarbonate. The reaction mixture is diluted with 50 ml of water andextracted twice with ethyl acetate. The aqueous phase is acidified to pH2 and extracted three times with ethyl acetate. The aqueous layer isbrought to pH 7.4 by addition of 5% aqueous sodium bicarbonate and thesolution is passed through a XAD-4 resin column while eluting with waterfollowed by methanol. The product-containing fractions are evaporated todryness to give7-trifluoromethylthioacetamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid disodium salt.

7-Trifluoromethylthioacetamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid disodium salt is converted to the title compound as described inExample 1.

EXAMPLE 7

Reaction of the sodium salt of a cephalosporanic acid listed below:

7-(2,2,2-trifluoroethylthioacetamido)cephalosporanic acid

7-methylthioacetamidocephalosporanic acid

with 2-sulfomethyl-1,3,4-oxadiazole-5-thiol and sodium bicarbonate asdescribed in the procedure of Example 6 gives, after conversion of thesalts formed to the free acids, the following compounds of thisinvention as final products:

7-(2,2,2-trifluoroethylthioacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-methylthioacetamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid.

EXAMPLE 8

Reaction of a cephalosporanic acid listed below or its correspondingsalt:

7-(α-hydroxy-2-thienylacetamido)cephalosporanic acid

7-(α-carboxy-2-thienylacetamido)cephalosporanic acid

7-(α-sulfophenylacetamido)cephalosporanic acid

with 2-sulfomethyl-1,3,4-oxadiazole-5-thiol and sufficient sodiumbicarbonate to convert the acidic functions to the corresponding sodiumsalts by procedures described hereinabove gives, after conversion of theproduct salts to the free acids, the following compounds of thisinvention:

7-(α-hydroxy-2-thienylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-carboxy-2-thienylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(α-sulfophenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid.

EXAMPLE 9

When an equivalent amount of a chloroalkanoic acid ester listed below:

3-chloropropionic acid ethyl ester

4-chlorobutyric acid ethyl ester

5-chlorovaleric acid ethyl ester

6-chlorohexanoic acid ethyl ester

is substituted into the procedure of Example 1 in place of ethylchloroacetate and the resulting sulfo acids are converted to thecorresponding hydrazides which are subsequently treated with carbondisulfide to give sulfoalkylcarbonylhydrazinecarbodithioic acids whichare then cyclized, all as described therein, the following2-sulfoalkyl-1,3,4-oxadiazole-5-thiols are obtained as the correspondingpotassium salts:

2-(2-sulfoethyl)-1,3,4-oxadiazole-5-thiol

2-(3-sulfopropyl)-1,3,4-oxadiazole-5-thiol

2-(4-sulfobutyl)-1,3,4-oxadiazole-5-thiol

2-(5-sulfopentyl)-1,3,4-oxadiazole-5-thiol.

The thiol potassium salts are converted to the free acids as describedin Example 1.

Reaction of the potassium salt of a2-sulfoalkyl-1,3,4-oxadiazole-5-thiol listed above with7-D-mandelamidocephalosporanic acid sodium salt and one equivalent ofsodium bicarbonate as described in Example 1, followed by conversion ofthe product salt formed to the free acid, gives the following compoundsof this invention:

7-D-mandelamido-3-[5-(2-sulfoethyl)-1,3,4-oxadiazol-2-ylthiomethyl]-3-cephem-4-carboxylicacid

7-D-mandelamido-3-[5-(3-sulfopropyl)-1,3,4-oxadiazol-2-ylthiomethyl]-3-cephem-4-carboxylicacid

7-D-mandelamido-3-[5-(4-sulfobutyl)-1,3,4-oxadiazol-2-ylthiomethyl]-3-cephem-4-carboxylicacid

7-D-mandelamido-3-[5-(5-sulfopentyl)-1,3,4-oxadiazol-2-ylthiomethyl]-3-cephem-4-carboxylicacid.

EXAMPLE 107-Amino-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

To a mixture of 97 g (2.1 mol) of formic acid, distilled from anhydrouscopper sulfate, and 37.5 ml (0.4 mol) of acetic anhydride was added 25.0g (0.1 mol) of 7-aminocephalosporanic acid. The mixture was stirred atambient temperature for 0.5 hour, then evaporated to dryness. Theresidue was dissolved in ethyl acetate and the ethyl acetate solutionwas filtered and evaporated to dryness to give a residue which wasrecrystallized from ether-petroleum ether to give7-formamidocephalosporanic acid.

A mixture of 1.0 g (3.3 mmol) of 7-formamidocephalosporanic acid, 0.51 g(2.6 mmol) of 2-sulfomethyl-1,3,4-oxadiazole-5-thiol and 0.71 g (8.5mmol) of sodium bicarbonate in 15 ml of water is stirred at 65°-70° for3 hours while maintaining the pH at 7.0. The mixture is cooled,acidified to pH 1.0 with hydrochloric acid and extracted with ethylacetate. The extract is filtered and the filtrate is evaporated todryness to give a residue which is dissolved in methanol. The methanolsolution is filtered and ether is added. The precipitate is collected byfiltration and dried to give the title compound.

EXAMPLE 117-(4-Pyridylthioacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

(4-Pyridylthio)acetyl chloride (0.53 g, 2.8 mmol) is dropwise added to amixture of 1.0 g of7-amino-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid and 0.9 g (9.0 mmol) of triethylamine in 10 ml of drydimethylformamide. The reaction mixture is stirred for 1.5 hour at -10°,then it is warmed to ambient temperature and stirred for 1 hour. Themixture is filtered and the filtrate is diluted with 200 ml ofether-petroleum ether. The precipitate is collected by filtration anddissolved in water. The aqueous solution is passed through an AmberliteIR-120H resin column and the product-containing fractions arelyophilized to give the title compound.

EXAMPLE 12

Acylation of7-amino-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-caboxylicacid with an activated derivative of the following acids:

cyanoacetic acid

3-pyridylthioacetic acid

cyanomethylthioacetic acid

2,2,2-trifluoroethylsulfinylacetic acid

trifluoromethylsulfonylacetic acid

2-pyridone-N-acetic acid

4-pyridone-N-acetic acid

as described in the procedure of Example 11 gives the followingcompounds of this invention:

7-cyanoacetamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(3-pyridylthioacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-cyanomethylthioacetamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(2,2,2-trifluoroethylsulfinylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-trifluoromethylsulfonylacetamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(2-pyridoneacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-(4-pyridoneacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid.

EXAMPLE 137-(D-α-Formyloxyphenylacetamido)-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid

7-Amino-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid is reacted with the formate ester of D-mandeloyl chloride accordingto the procedure of Example 11 to give the title compound.

EXAMPLE 14

An injectable pharmaceutical composition is formed by adding sterilewater or sterile solution (2 ml.) to 500 mg. of7-D-mandelamido-3-(5-sulfomethyl-1,3,4-oxadiazol-2-ylthiomethyl)-3-cephem-4-carboxylicacid sodium salt.

Pharmaceutical compositions of the other antibacterial compoundsdisclosed above may be formulated in a similar manner.

What is claimed is:
 1. A compound of the formula: ##STR8##in which: n is1 to
 5. 2. A compound according to claim 1, said compound being2-sulfomethyl-1,3,4-oxadiazole-5-thiol.